Yoshikazu Hamaguchi

Phase Transition in SnTe with Low Carrier Concentration

The phase transition in SnTe was investigated on a single crystal with low carrier concentration (0.88×10 20 cm -3 ) by the neutron diffraction method. A second-order phase transition takes place a...

Antiferromagnetism in disordered B.C.C. Cr-Mn Alloys

The neutron diffraction, electrical resistivity and magnetic susceptibility measurements on b.c.c. Cr-Mn alloys containing manganese from 7.0 to 25.3 atomic percent have shown that the alloys are antiferromagnetic but disordered atomically. The obtained results are shown to be compatible with the theoretical conclusions from the spin density wave model.

Experimental Test of Rigid Band Models for Cr by Means of Cr-V-Mn Ternary Dilute Alloys

Electrical resistivity and powder neutron diffraction patterns for Cr-V-Mn ternary dilute alloys have been measured at various temperatures. From the measurement an estimation is made on the Neel temperature, spin arrangement, average magnetic moment and wave vector of spin density wave. The ternary data are compared with those already obtained on the Cr-V or Cr-Mn binary dilute alloys. This comparison is made on the same scale of effective concentration, i.e. the manganese concentration subtracted by the vanadium concentration in units of atomic percent. The results have shown that there is a good agreement between the data on the ternary and binary alloys. This fact supports the validity of rigid band approximation. The wave vector was evaluated using the three models which were proposed for explanation of the properties of chromium metal. The results were compared with the experimental results.

X-ray study on a phase transition of U4O9

Abstract Some features of the transition of U 4 O 9 were investigated by means of X-ray diffractometry. Transition temperature of the U 4 O 9 phase varies from 65 to 96°C with O/U ratios and, at the transition, a notable increase in the intensity of superlattice reflection of U 4 O 9−y with temperature was observed.

Determination of the Exchange Integrals in β-MnO2

Magnetic susceptibility and specific heat of the β-MnO 2 powder specimen have been measured in the range 20 to 300°K and 77 to 100°K respectively. The measurements have also been made for the paramagnetic inelastic neutron scattering at room temperature by using time-of-flight method. The values of the Weiss temperature, of the Neel temperature and of the average full width at half maximum of the neutron energy distribution (Gaussian) have been determined as 1050°K, 92°K and 13 meV respectively. The exchange integrals ( J n ) are determined by combining these experimental data with the theoretical relations between exchange interactions and physical properties and by assuming J 1 / J 2 =1.60: J 1 =8.9 (antiferromagnetic), J 2 =5.5 and J 3 =-1.3°K, where J 1 is the exchange integral between nearest neighbours (in the direction), J 2 acts between next nearest neighbours ( direction) and J 3 refers to third-neighbour coupling.

Magnetic Structure of TbCu1-XZnX

Magnetic structure of TbCu 1- X Zn X system with the cubic CsCl type structure has been studied by neutron diffraction and magnetic measurements. In Cu-rich region ( X <0.5). the antiferromagnetic structure is conserved, which is TbCu type with (π π 0) mode. When X increases further, the magnetic state suddenly transforms to a ferromagnetic state with canted spin arrangement of which antiferromagnetic mode is (π π 0). In the region with the canted spin arrangement (0.5< X <0.7), the magnetic state approaches to a simple ferromagnetic state with increasing temperature, and transforms not only to a complete ferromagnetic state with increasing temperature, and transforms not only to a complete ferromagnetic state, but also directly to a paramagneticstate. This magnetic phase diagram and properties are fairly well explained by the theory based on the s-f exchange interaction with the low density 4s-electrons, assuming the electronic band structure of YZn.

Helical magnetic structure in CrB2

Abstract A cycloidal magnetic structure was discovered in CrB2 by neutron diffraction using a thin single crystal plate prepared with natural boron. The propagation vector was determined to be τ = 0.285 τ110. The magnetic moments of a magnitude of 0.5 ± 0.1μB turn in the a−c plane.

Ferromagnetism of the Intermetallic Compound UFe2

The magnetic properties of UFe/sub 2/ were investigated at 300 deg K to 100 deg K. Metallic uranium and electrolytic iron, each 99.9% pure, were melted together in a vacuum and held at 1300 deg C for one hour, after which they were cooled to room temperature. Further cooling revealed evidence of ferromagnetism at 195 deg K. (L.N.N.)

Magnetic Properties and Magnetic Phase Diagram of bcc Cr-Fe-Mn Alloys

Magnetization measurements have been performed on bcc Cr 80- x Fe 20 Mn x (3.6≤ x ≤38.4) and Cr 75- x Fe 25 Mn x (5.0≤ x ≤29.1) alloys between 6 and 300 K using a SQUID magnetometer. The ferromagnetic and spin-glass transitions are observed in these alloys. The magnetic phase diagram of bcc Cr 80- x Fe 20 Mn x and Cr 75- x Fe 25 Mn x alloys are determined using the Curie temperature, T C and spin-glass temperature, T g decided in this work, and the Neel temperatures, T N reported on the same alloy system. The spin-glass phase spreads for a wide concentration region in the present Cr–Fe–Mn ternary alloy system. The magnetic moment of the ferromagnetic Cr–Fe–Mn alloys at T =0 is compared with Slater-Pauling curve.

Neutron Scattering Measurements in Chromium near the Néel Temperature

Yorihiko Tsunoda, Yoshikazu Hamaguchi, Nobuhiko Kunitomi, Neutron Scattering Measurements in Chromium near the Neel Temperature, J. Phys. Soc. Jpn. 32, pp. 394-399 (1972)